The Diocese of Zahum–Hercegovina was founded by Saint Sava in 1219, while the autocephalous Serbian Archdiocese was first being organized. The Diocese of Hum, as it was initially named, had its See in Ston, centered on the Church dedicated to the Most Holy Theotokos. The first Bishop of Hum was Ilarion, and among his well-known successors were Sava II (son of King Stefan the First-Crowned, and whose secular name was Predislav) till 1264; then Bishop Jevstatije (circa 1300), Jovan (circa 1305); and Danilo (1316–1324), the subsequent Serbian Archbishop. During his reign, the Ban of Bosnia, taking advantage of conflicts between King Stefan of Decani and Prince Constantine over the throne, took Hum; Danilo was forced to flee, and establish the See of his Diocese in the Monastery of Saint Peter (most probably the one on the Lim River, an endowment of Nemanja’s brother Miroslav). Danilo was succeeded by Bishop Stefan.

Having been incorporated into the Bosnian state during the rule of King Tvrtko I, Monastery Mileseva became the See of the Bishops of Hum and Bosnia. Since the 15th century, when the title "Herceg of Saint Sava" was conferred upon Stepan Vukcic Kosaca and Hum was renamed Hercegovina, that Diocese was also named the Diocese of Hercegovina. Two Bishops of Hum (Mileseva) are known of before the fall of Hercegovina to the Turks: the first being the one who crowned King Tvrtko I in Mileseva in 1337; the second was David, whose name is mentioned in 1466 and 1471.

Following the fall of Hercegovina under Turkish rule, the See was frequently moved, finally to settle in Monastery Tvrdos near Trebinje. From that period the following Bishops of the Diocese of Zahum-Hercegovina are known: Jovan (1508–1513) and Visarion, restorers of Monastery Tvrdos (1508); then Marko (1524), Maksim (1532), Nikanor (1546), Antonije (1570), Savatije (1573–1585), Visarion (1592), Silvestar (1602) and Leontije (1605–1611).

Subsequent events caused the division of the Diocese into two: the Diocese of Trebinje, with its See in Monastery Tvrdos; and the Diocese of Mileseva, frequently referred to as the Diocese of Polhercegovina or of Peter, after Saint Peter’s Monastery on the Lim River, where its See was even under the Turks located for some time. When the Turks turned the Monastery of Saint Peter into a mosque, in the second half of the 17th century, the See was moved across the Tara to Niksic, formally the town of Onogost.

The troubled past of that area influenced the changing of the borders of those Dioceses, unified in the 18th century after the Peace Treaty of Belgrade in 1739. The Bishops of Hercegovina, or Trebinje, whose names are recorded in that per